The present invention relates to a control method for a multi-window image display which is suitable for displaying document image data such as charts, seal impression, maps and business slips.
A bit map display is usually used as an image display connected to a computer: a bit map is also called a display memory and stores data to be displayed at lattice crosspoints of two-dimensional images. By dividing a screen of the bit map display into a certain number of areas (windows), it is possible to simultaneously display a plurality of image data and independently control them. It is called a multi-window display and has an advantage of easiness of retrieval and comparison of the image data.
The concept of the multi-window display has been known and several applications thereof have been known. Many of them relate to a character display and are intended to display coded character data such as alphanumeric characters as described in an article "A time-sharing display terminal session manager" by J. M. McCrossion et al, IBM System Journal, Vol. 17, No. 3, 1978, pages 260-274.
As another form of the multi-window display, "a multi-graphic display" has been proposed (see Japanese Laid-Open Patent Application 54-75225). In the proposed display, one screen of display data is divided into blocks which are chained with each other to allow the editing of the display data, and the individual display data can be rotated, shifted or scaled block by block. The data to be handled is graphic data such as lines or arcs.
A third category is the multi-window display for the image data. As one example thereof, a dual-screen television which can simultaneously display two programs has been proposed (see Nikkei Electronics, Feb. 26, 1977, pages 127-132). The dual-screen television composes television screens by the timing control of a video signal and has no capability to interactively carry out scroll of the image data, or creation, deletion, movement or size modification of the window.